Enercare review: Regular maintenance check

I have an annual maintenance plan with Enercare that I pay for. They came last week (June 21, 2021) to check the furnace and sent a report afterwards saying that our furnace was "100" in terms of performance. Since the technician left however, we now have a "rattle" sound coming from our furnace. I called Customer Service today (June 28th) to ask for the technician to come back and I was told that it would now cost me $99 to pay for the technician or I could pay to upgrade my plan to include ongoing technical support. I would like them to come back to fix "for free" whatever they have done to the furnace to cause it to make a noise. I was told by Customer Service rep that this was not an option.